Typically, rotary wing aircrafts like helicopters are sustained by a rotor, rotating about a vertical rotor shaft, generating lift or upward thrust. In a conventional helicopter the thrust from the rotor can be controlled by changing the pitch angle (or in short: the blade pitch) of the rotor blades. The blade pitch is in the field of propeller aerodynamics defined as the lateral angle between the blades and a reference plane perpendicular to the rotor shaft axis, measured perpendicular to the longitudinal axis of a rotor blade.
By collectively changing the blade pitch of all the rotor blades or by changing the rotational speed of the rotor, the helicopter can be controlled in the vertical direction. The horizontal direction of flight and the stability of the helicopter, however, are controlled by cyclically adjusting the blade pitch of individual blades. Cyclically adjusting the pitch means that the blade pitch of each rotor blade is adjusted from a maximum in a particular position of rotation to a minimum at the opposite side. This causes the lift in one part of the rotation to be larger than in other parts, whereby the rotor is tilted with respect to the reference plane. When the rotor (and helicopter) tilts like this, the initially vertical thrust also tilts, and therefore gets a horizontal component pulling the helicopter in the desired direction.
Normally, a helicopter must be actively controlled by a well trained pilot or from gyroscopic sensors and computers. The necessary means to varying and controlling the pitch angle of each blade are normally complicated, expensive and add weight to the helicopter. The blade pitch is typically controlled via a swash plate connected to servos. Because the servos need to be positioned accurately in order to control the helicopter, they are complicated and expensive.
Using magnetic actuators would be a simpler and less expensive way of manipulating the swash plate to control blade pitch. Magnetic actuators, however, are ideal to control the actuation force but do not have the position accuracy normally required in a traditional helicopter rotor system. Some rotor systems also provide passive stability to the helicopter, but these systems are often difficult or impossible to combine with precise control over the blade pitch.
To maintain passive stability of a helicopter and at the same time allow precise control by using low cost magnetic actuators would require a completely new rotor system.